In recent years, the production amount of semiconductor devices has shown a steady increase, and a reduction in production cost thereof has become an important task. For bonding of semiconductor chips to a lead frame, there is a method of using, as an adhesive, an inorganic material such as gold-silicon eutectic material or the like. This method is expensive and may incur breakage of semiconductor chips caused by thermal stress; therefore, a method of using a die-attaching paste (a paste-like adhesive) obtained by dispersing a filler in an organic material or the like, has become a main stream.
Meanwhile, with respect to the reliability of semiconductor devices, solder cracking resistance is particularly important. A die-attaching paste capable of giving a semiconductor device having satisfactory solder cracking resistance needs to have a low modulus of elasticity for relaxation of the difference in linear expansion coefficient between semiconductor chips and lead frame.
In recent years, the requirement for solder cracking resistance has become strict; as solder has become lead-free, the reflow soldering conditions have been switched from 240° C. to 260° C.; in order to meet this temperature increase of 20° C., a lower elastic modulus has become necessary. For a lower elastic modulus, die-attaching pastes using a low-stress substance (e.g. a rubber) have heretofore been known; however, they are unable to satisfy the recent requirement for solder cracking resistance and an improved die-attaching paste is needed.